Research On The Brewing Microorganisms And Body Flavor Of Maotai-flavor Liquor Based On Microbiology

The unique characteristic of Maotai-flavor liquor is mainly derived from the complex fermentation process and microbial community structure.The stacking fermentation process is one of the special processes of Maotai-flavor liquor.It can collect a large number of microorganisms and increase the types and contents of flavor substances,which is conducive to the formation of Maotai-flavor liquor characteristic.Studying the microbial consortium during the staking fermentation of Maotai-flavor liquor is the basis for analyzing the fermentation mechanism and flavor formation of Maotai-flavor liquor,but the results obtained by single method are limited.Microbiomics is a new subject based on microbiology,functional genomics,metabonomics and so on.For traditional solid-state fermentation,the application of microbiomics strategies can reveal the changes of microbial community structure in the natural fermentation process and the effect of the changes on liquor flavor.Based on microbiomics,high-throughput sequencing technology coupled with culturable means were used to study the microbial community structure in fermented grains of Maotai-flavor liquor during three,four and five rounds of stacking fermentation.The flavor characteristics of aroma-producing bacteria and their combinations were preliminarily explored.The following results were obtained:(1)Using high-throughput sequencing technology,17 bacterial and 5 fungal phyla were detected in fermented grains of Maotai-flavor liquor in three,four and five rounds.Among them,Firmicutes was the dominant phylum of bacterial,and Ascomycota is the dominant phylum of fungal.At the generic level,237 genera of bacteria and 230 genera of fungi were obtained.Among them,14 genera of bacteria were considered to be important bacterial genus,and Acetobacter,Staphylococcus played a negative regulatory role in the system while other genera played a positive regulatory role.Meanwhile,16 genera of fungi were the important fungi genus,and they play a positive regulatory role in the system.(2)Using culturable technology,a total of 221 strains of bacteria,155 strains of yeast and 81 strains of fungi were isolated from fermented grains in three,four and five rounds of stacking fermentation of Maotai-flavor liquor.The molecular identification and homology analysis showed that 24 kinds of bacteria,13 kinds of yeast and 20 kinds of fungi.Different bacteria belong to to 11 genera,among which Bacillus,Brevundimonas and Micrococcus were the main genus of bacteria.Different yeasts belong to 8 genera,and the genus Saccharomyces and Pichia were the main genus of yeast.The molds belong to 15 genera,respectively,of which Aspergillus and Penicillium were the main molds.(3)Through solid-state fermentation and sensory evaluation,the selected strains mainly presented fermentation aroma,raw material odor,typical aroma and unpleasant odor during solid-state fermentation.With the increasing of fermentation time,raw material fragrance had lower aroma intensity,while the aroma intensity of fermented aroma,aged aroma,green aroma and caramel aroma changed little during fermentation.The flavor profiles of different strains were different and similar,of which 15 strains have typical aroma,4 strains present unpleastant odor,and 5 strains had no special aroma.(4)According to the aroma characteristics,20 strains were selected for flavor determination by HS-SPME coupled with GC-MS.A total of 253 flavor compounds were detected from 20 single strains,including 71 aromatic compounds,41 alkanes,49 aldehydes and ketones,2 terpenes,16 nitrogencontaining compounds,21 alcohols,2 furans,2 sulfide,31 esters,5 acids and 13 others.The substances produced had no differences in classification,mainly aromatic compounds,alkanes,aldehydes and ketones,nitrogencontaining compounds,alcohols and esters.According to the chemical classification of metabolites in different strains,the content of nitrogen compounds were the highest,followed by alkanes,aldehydes,ketones and furans,and terpenes and sulfides were the lowest.In addition,4-ethyl guaiacol was a characteristic compound in the fermentation of Bacillus pumilus.(5)According to the evolutionary relationship of microorganisms and sensory evaluation,five groups were established through 3 genus and 10 strains.The solid-state fermentation showed similar aroma characteristics,mainly showing raw material aroma,typical aroma and unpleasant aroma.Among the different bacterial groups,aromatic compounds had the most classes of compounds,followed by alkanes,aldehydes and ketones and alcohols.Compared with the single strain before the combination,there were no significant differences in the types of aroma compounds in the five groups,but there were significant differences in the content.